Freezing for the cause: Fuji XF Lens Testing

Astronomy is often a hobby of extremes – travelling to extreme’s for the darkest skies, pushing optical and camera equipment to the extremes in order to capture the faintest most distant worlds, and extremely cold winter nights for those perfectly clear and stable skies.

Recently I had the opportunity to test a bunch of X-Mount lenses for my Fuji X-E2 thanks to Camera Electronic in Perth. Having the lenses meant I wasn’t going to miss a clear night, even if it meant it was going o be a very cold one!

These were the lenses: XF 15mm F/2.8, XF 18mm F/2 and XF 18-55 F/2.8-4. They are shown together with my existing Samyang 12mm F/2 and Fuji XF-27mm pancake below.

Working with the three lenses on three different nights, and carrying my XE-2 around for the week mostly with the XF 15-55 F/2.8-4 attached, the following would be my summary of how the lenses performed:

XF 14mm F/2.8. This lens was a pleasure to use. The focus ring is very nice and easy to control with fantatic feel, much more so than my XF-27mm or Samyang 12mm. The lens stops only very slightly past infinity (and does have a stop as opposed to my XF 27mm) so focusing for infinity was somewhat easier than some lenses, as distance from stop was quite easy to train my fingers to remember. Coma was significant in the far corners, but only the far extremes and to remove almost all coma you would crop to about 88% original frame. The lens has no issues with chromatic aberration or false colour that I could discern, and no issue with vignetting either. Of all the lenses this lens remains the sharpest in all corners, even though exhibiting coma.

Fuji XF 14mm F/2.8 at F/2.8 bottom left crop

XF 18mm F/2. This lens ended up being a bit of a nuisance to be honest. I found it difficult to manually focus on the stars, and whenever I was using it wondered why I wouldn’t just switch back to the more pleasing 18-55 (see notes below). Of course it is F/2 which makes it slightly faster, but that didn’t outweigh the usability issues I had with it. Coma is quite noticeable in the corners, with lager flare and a more distracting seagull and cross shapes than the 14mm. To remove most of the coma I found I needed to crop down to about 84% of original frame size. I think a large part of the manual focus difficulty came from the increased coma this lens exhibited. The motor movement of the lens was a bit jerky too. There is a some blue chromatic aberration but it is not a significant issue.

Fuji XF 18mm F/2 at F/2 bottom left crop

XF 18-55 F/2.8-4. This lense was my favorite of the three even though it was not perfect from the choma and edge sharpness perspective. The lens was easy to manually focus and exhibits relatively well control coma. In fact in 3 out of the 4 corners coma is almost non-existent (see first example below) and far better than the other lenses. What’s better, the coma which exists is of a more circular shape than the other lenses making it much less noticeable at normal viewing sizes. Cropping out the coma to a reasonable clean field leaves you with about 90% of the frame. Interestingly in all my testing almost all of the coma was in the top right of frame, with the rest of the image extremely clean. This made me wonder how a different copy of the same lens would behave (if there was an element not quite parallel in this particular lens). This lens exhibited the most softness at the corner, only in the top right. The lens autofocuses beautifully, has a great zoom range, is nice and compact for a zoom of this range, and overall a real pleasure to use. Zooming the lens in to F/4 the field is flawless with no coma, no chromatic aberration or false colour, no vignetting and no softening of the edges leaving only pinpoint stars across the field. Remember though at 55mm this lens is F/4 which is about as slow as you want to go for an astrophotography lens.

Fuji XF 18-55 F/2.8-4 at F/2.8 bottom left crop – Check out that perfect field of stars!!!

Fuji XF 18-55 F/2.8-4 at F/2.8 top right crop. Not so pretty in the top right, but you could work with that (for example using composition to reduce its impact).

For comparison I will include a comparable test of my Samyang 12mm F/2. Comparing to the Fuji XF lenses above this lens does in the end still have less coma with limited chromatic aberration. Cropping out the noticeable coma in this lens still leaves you with 91% of the frame, and to be honest I mostly don’t bother doing any cropping. The coma exhibited by this lens is relatively unnoticeable because like the 18-55 F/2.8-4 it is quite tight and not great big spikes or seagulls (as shown in the XF 18mm F/2 and XF 14mm F/2.8). This lens is unique when it comes to manual focus however, in so much as the focus ring is extremely stiff which makes small tweaks of focus sometime tricky and is a little disconcerting when the lens rotates slightly on the lens mount due to the force exerted. The stiff focus is quite common with this lens (google and you will see many people asking about it). The advantage of the stiff focus is that you can to a greater extent “set and forget” the focus during a night of astrophotography because you are unlikely to knock it out.

Samyang 12mm F/2 at F2 bottom left crop

Samyang 12mm F/2 at F/2.8 top right crop

Testing notes:

Sample images shown are 1000px x 800px crops from 100% sized images.

All comments refer to the lenses being used at their fastest aperture. Stopped down all lenses improved their image quality significantly, but this is of little benefit to astrophotography where wide-open is key.

Each lens was tested on the same nights.

All images shown above are as-shot from in-camera JPG with no adjustments.

Test field of view did vary between lenses due to the nature of needing to re-frame for focusing on bright stars, but needing a mix of bright and less bright stars for long exposure testing.

Every lens performs different in different corners of the FOV, to varying degrees. As such the results vary depending on which corner you examine. I have provided the best cross section reasonable in a concise review.

All lenses have pinpoint stars throughout the middle 1/2 the FOV.

It is worth noting that astrophotography is a particularly harsh test for camera lenses. Ideally you want pinpoint stars across a wide field, and that is tricky to achieve with a lens. Lenses that are often rated very well for landscape and portrait photography fail at astrophotography. WIth this in mind, the comments here should only be considered for astrophotography use – it may be that the lenses perform very differently under other criteria. All the Fuji XF lenses tested here performed better than I have seen many other camera lenses perform, including some Canon L lenses for example.

So, what lens will I be buying for my Fuji XE-2 now then? Well the 18-55 F/2.8-4 is the lens I want. The lens was a joy to use for general terrestrial photography (street, landscape and portrait) as well as astrophotography. The top right corners is bad, but remainder of the field almost perfect to extremes. I would love to test a different copy of this lens as I suspect (hope) the top right is an anomaly of this particular lens. If I did not already have the 12mm Samyang and was a keen Fuji user looking for a wide angle, the 14mm is a nice lense and somewhat comparable to the 12mm however for the advantges of autofocus and better manual focus you would sacrafice some corner quality compared to the Samyang.

I hoped that the Samyang 12mm would be mothballed by the Fuji XF 14mm, as I like the idea of autofocus and softer manual focus for daytime use. However with the results above I will be sticking with my Samyang 12mm for wide angle situations for now, perhaps until I test the XF 16mm.

So what’s this about the cold then? Well, even in the mild temperatures of Perth (winter nights down to about -2c inthe hills at worst) it can be very cold doing astrophotogrpahy! Here I am out testing the lenses kitted out in my ski gear to keep warm! It makes a real difference to how long you can stay outside doing astrophotography when you are comfortably warm, I can tell you.

Roger doing astrophotography on cold winter night. 2 degrees C at the time, and standing out in the open doing astrophotography for hours.

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Started by Roger Groom in 2003 Astro Photography Australia sells prints, copyright use, acrylic photo blocks and mugs of astrophotography. Every print is high quality made to last, making great gifts.

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